The Universal Serial Bus (USB) standard was initially offered in the mid-1990's as an easy-to-use universal interface for a Personal Computer (PC). Since then, USB has gained widespread acceptance. From the user perspective, the benefits of USB include universal plug-and-play and relative ease-of-use. When a USB peripheral is plugged-in to a USB port on a PC, the system will auto-detect and auto-configure the device. In most cases, there is zero user intervention. This is a significant improvement over the prior technology where a user had to open the PC to install a component. The USB interface also eliminates the need for multiple I/O standards, thereby simplifying PC connectivity for the consumer as well as simplifying manufacturing for the PC Original Equipment Manufacturers (OEMs).
The original USB specification has evolved over time to meet the needs of industry, resulting in two versions available today. The USB interface is described as version 1.1 “Universal Serial Bus Revision 1.1 specification” and version 2.0 “Universal Serial Bus Revision 2.0 specification,” both documents are available at the USB website http://www.usb.org/developers/docs/.
The first version of the USB, USB 1.1, focused on making computing easy for everyone, and it has been very successful in achieving this goal. However, the bandwidth of USB 1.1 is insufficient for some applications. With a top speed of 12 million bits/second (mbps), the system performance could occasionally become sluggish if multiple multimedia devices were attached to one USB port.
To address this problem the USB specification was updated to version 2.0 to improve the performance and usability of PC peripherals, opening the door to a world of high-performance/high-bandwidth applications such as mass storage, digital video, and broadband access. A further advantage is that all of these applications and many others can run simultaneously. The speed of USB 2.0 has been increased to 480 mbps, a 40× improvement over its predecessor. Both the USB 1.1 and USB 2.0 interfaces are wired interfaces, as they use a cable between the host (for example a personal computer or PC) and the USB peripheral.
The USB devices/peripherals may include devices such as printers, scanners, keyboards, a mouse, joysticks, digital cameras, digital video cameras, data acquisition devices, modems, speakers, telephones or video phones, storage devices such as ZIP drives, or any other peripheral or computing device.
Wireless connection of devices to computers, and wireless networking of groups of computers is one of fastest growing segments of the PC industry. Current and emerging technologies in this field include IEEE 802.11 (also known as ‘WiFi’), Bluetooth, and Cypress Semiconductor's proprietary Wireless USB standard. The WiFi specification is at: http://standards.ieee.org/getieee802/802.11.html. The Bluetooth specification is at: https://www.bluetooth.org/foundry/specification/docman/.
While effectively meeting certain application-specific needs, these technologies do not generally offer the combination of versatility, ease of installation and use, and bandwidth of the now dominant wired USB standard. Disadvantages of the ‘WiFi’ IEEE 802.11 standard for wireless PC peripherals include the fact that it uses significant processing power for every node, which is costly. WiFi also uses a complex network set-up operation at both ends, it is not a simple ‘plug and play’ operation. In addition, WiFi cannot transparently convert a wired USB peripheral into a wireless peripheral. Disadvantages of the Bluetooth standard for wireless PC peripherals include the fact that it has limited bandwidth which may not be adequate for printing or file transfer, and it cannot transparently convert a wired USB peripheral into a wireless peripheral. Bluetooth also has lengthy and complex setup.
An advantageous wireless technology for connecting peripherals to PCs (and other USB hosts) would retain all the advantages of USB, while allowing wireless connection of devices to hosts. One potential means of achieving this aim would be to simply transmit and receive USB signals wirelessly, instead of over cables, retaining the USB protocol, timing, device model, etc. However, there is an obstacle to such an implementation in the form of the short response times USB devices are required to achieve, which is the reason for the five meter (m) maximum USB cable length.
Although radio frequency (RF) signals propagate somewhat faster through air than electrical signals do through cables, typically radio transmitters and receivers introduce additional propagation delay greater than that typical of line drivers and receivers, such as USB transceivers. Furthermore, many signaling schemes used in wireless systems introduce further group delay. For example, encoding multiple bits in a single transmitted symbol necessarily involves delaying the symbol by one bit period for each bit in the symbol, so the first bit in a 4 bit per symbol above 1 signaling scheme has an intrinsic 3 bit-period delay.
In some cases, the number of bits per symbol may change dynamically in responses to changes in bandwidth, signal-to-noise ratio changes, and changes in the presence of interfering signals. Additionally, usage models for devices connected wirelessly are different from the desktop usage model which USB assumes. For example, wireless devices may be moved during use to a greater extent than is possible with wired devices.
As opposed to USB cables, in the case of wireless connections, there is no predefined physical limit to the distance between the USB host and the USB peripheral device. Further, the physical distance between the USB host and the USB peripheral device may change during use. In the wireless case, multiple peripherals will typically connect individually to a base station over multiple dedicated wireless links (this is analogous to each “wired” peripheral connecting over separate long cables), rather than multiple peripherals connecting by cable to a remote wireless hub which would then communicate with the base station using a single wireless channel.
The present invention addresses this and other problems associated with the prior art.